Conventionally, such a structure includes an energy storage capacitor in series with a diode and connected to the source of energy.
The capacitor is also connected to the ignition spark plug through a gas-filled spark gap in order to be discharged through the latter and for generating sparks.
Studies have been conducted for very many years in order to replace this gas-filled spark gap with controlled semiconductor switching units, such as for example silicon controlled rectifiers.
In order to have an explanation on the reasons for these studies, reference may for example be made to document FR 2 636 678.
Among other reasons, it will be noted that gas-filled spark gaps pose problems of aging and modification of the ignition voltage.
Further, they use gases containing radioactive elements.
Other problems exist and an exemplary solution to some of them will be found in document FR 2 695 432.
This field of ignition generators for this type of applications is a field which has given rise to many studies and too many patents, from among which mention may be made of documents U.S. Pat. Nos. 3,515,937, 5,032,969, 5,053,913, 5,852,381, 6,104,143, 6,191,536, 7,768,767, US 2013/0025255, US 2014/0176003 and WO 2013/164 816.
But none of the systems described in these documents give entire satisfaction.
In particular it is known that when the gas-filled spark gap is replaced with a controlled semiconductor switching unit, one is confronted with a problem called thermal runaway.
In this respect, it should be noted that the operating conditions of this type of generators are extremely difficult.
Indeed, the latter are placed in proximity to the turbine and are therefore found in an environment with a very high operating temperature, i.e. of more than 120° C.
Now, the semiconductor switching units have a leakage current during the charging of the storage capacitor which increases with their operating temperature.
The increase in the leakage current, consecutive to the increase in the operating temperature of the turbine and therefore of the generator, is expressed by self-heating of the semiconductor switching unit of the latter, which is itself expressed by an increase in the leakage currents, and so forth.
This phenomenon is called thermal runaway and, as a general rule, is expressed by the destruction of the semiconductor switching unit and by a failure of the generator.